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Last week, a few moments away from ordering a well regarded sub, I stumbled across steve nn's Dayton Titanic 15" MKIII kit thread which has steered me to the DIY route. After evaluating my needs aided with the driver modelling program WINISD Pro I have pencilled out a plan of attack and am soliciting a little feedback to enlighten me of any errors or omissions of material importance.

I've decided to build two subwoofers each with an finished internal volume of 6.5 cubic feet, each housing one Dayton Titanic 15" driver. I chose this design after being intrigued by steve nn's posts on the Dayton kit but recognizing that his kit apparently suffers primarily in two areas: 1/ FR drop off below 25hz and 2/ distortion at/below the same frequency.

More than doubling box size flattens the response, achieving a relative increase of about 3dB at 20Hz. Additionally, modelling driver excursion in this box size indicates a power amp of approx 200 watts into 4 ohms need be used to prevent over-excursion. While the driver still exceeds XMAS at about 10 Hz, further modelling indicates the natural roll-off below 20Hz of the amplifier I have in mind will maintain the drivers excursion at approx 73% of it Xmas between 5-10Hz, 80% at 20Hz and 60% at 30Hz.

Employing two subs approximately halves the driver excrusion required to produce single box SPL"s below 50 Hz and this is where I trust large gains in sound quality will be achieved over the kit.

So it appears running two 6.5 cu.ft subs powered with perhaps a Crown XLS-202b will have the same potential maximum SPL output as Daytons kit (which I'm confident will produce satisfactory SPL's in my room) while offering 3dB better response at 20 hz, all this with half the cone excrusion helping to keep things cleaner sounding and with a cost only slighty above the price of one $688 kit. I should note my room adds gain all the down to 10 Hz so am confident the Dayton driver (even with the small box relatively steep roll-off) will work well in this configuration.

Now, I understand these drivers won't elicit ooohs and aaahs from the masses but the price is right and by all indications will suit my needs well. That's the plan, if need be I will add a HP filter or FBD but would rather avoid this if possible but obviously will take some time to make the final determination.

If anyone can identify any glaring issues with this plan I'd appreciate the feedback.

Without having seen the models, your plan looks good, and well thought out. Looking at your size, it doesn't look like you included fill in your calculations. With heavy fill, I bet you could build the box smaller and acheive the same Q. Or, you can build it you planed size and lower the Q even more with fill. Bigger is always better.

The SoundSplinter RL-P15 reportedly are a better driver than the Titanic. The new Ascendant drivers may also be better. Titanic is reportedly good, but there are better drivers out there.

Note that Steve sent back the Titanic, and got two RL-P15s. I also like my RL-P15s. :)

Correct, fill was not included in the design. I wish to achieve my objectives without employing "tricks", therefore no fill, PEQ, filters etc. While it may not be achievable I'll start with a simple bare bones plan and screw up the signal more as I go along if required to achieve greater SPL's or acceptable response.

The large box also keeps the "I required more SPL" option open by allowing room for adding another driver to each box in which case some stuffing may then be advantages.

I did take a look at the Soundsplinter driver and while it has higher Xmas therefore can handle more power, and should offer less excursion induced distortion at equal SPL's than the Dayton, the FR appears to be a little steeper as well. I would predict that should Steve measure the response of the Soundsplinter in a 3 cu.ft box may show relatively higher roll-off below 80Hz than the Dayton driver. While the Soundsplinter should have less distortion, assuming that higher SPL is not the goal but instead greater headroom, this advantage should become less relevant to the final SQ as more drivers are added to the mix, therefore I'm thinking that for my purposes the differences between the two may not justify the additional cost in drivers and box construction. (To achieve a Qtc of .58 the Soundsplinter requires an 8 cu.ft box while the Dayton 6.5.)

Regardless of the general responses the programs indicate and speculating on my part I've been searching for posts by Steve for some ITR (in the room) objective and subjective comparisons between the two but haven't seen anything yet.

Thanks for the DIY forum heads-up, I didn't know it existed. I'll ask the mods to move my post.

I'll start with a simple bare bones plan and screw up the signal more as I go along if required to achieve greater SPL's or acceptable response.

Hey Hugh,
This sure sounds interesting. After experiencing the 15" MKIII driver, I'll be sure to be following what you come up with. With going on the larger side.. you can always work backwards if you decide by adding hard-fill to make the enclosure smaller if you deem it's needed.

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I've been searching for posts by Steve for some ITR (in the room) objective and subjective comparisons between the two but haven't seen anything yet.

I haven't really had to much to say until I get my thoughts/numbers totally firmed up. I just finished my second unit a few days ago minus the veneer. I've been playing around with fill and still have some other options (in fill/lining) that I would like to try out. As I have been writing this post the BASSIS just showed up..so it's still a work in progress.

I am very interested in your decision to go large though. I thought I was pushing things as it was with 3.8 though from speaking to Mike over at SoundSplinter.

Quote:

(To achieve a Qtc of .58 the Soundsplinter requires an 8 cu.ft box while the Dayton 6.5.)

The FS is a little lower, but are you factoring the D2 and not the D4 RL-p? Anyway I like your approach and again am very interested in what you come up with. :cool:

I discussed this issue of Titanic going slightly deaper with ThomasW. One of the reasons for getting the RL-P15 driver is that it can handle more EQ and LT to increase the low end. So yeah, the Titanic will go slightly lower when placed in the same box, but the RL-P15 will allow you to go lower and have more power if you use EQ or LT.

Understand your goals. Sounds good. You will want a little fill to absorb the high frequencies. I beleive that Thomas just told Steve this.

With being able to adjust my Q with the BASSIS, I'm finding it incredibly useful for this alone. I'm still acclimating myself with it, but I'm solid down to 15hz now along with great SQ. If my disk went lower, I would have plenty to measure. I had good SQ prior, but it was a little off at at a certain FR. I'm still not sure what to attribute that to though.

Funny thing about the fill..it seamed to enhance the higher FR??? I have a pound or so in one sub and the other is empty minus the driver and braces. I'm going to check out the liner (acoustic foam) since I have five sheets.

Ryan> Listen to your subs as caefully as you can...listen for what you don't like and try to react the best you can. No sub is perfect along with the subject material. Of course it's good to listen for what we do like, but theres always room for improvement, or trade offs that need to be worked around for bass to write home about. ;)

Hey Hugh,
This sure sounds interesting. After experiencing the 15" MKIII driver, I'll be sure to be following what you come up with. With going on the larger side.. you can always work backwards if you decide by adding hard-fill to make the enclosure smaller if you deem it's needed.

I think from a practicality standpoint if push comes to shove the idea of making the enclosure relatively smaller by adding more drivers is the way to go. ;)

Quote:

Originally Posted by steve nn

I am very interested in your decision to go large though. I thought I was pushing things as it was with 3.8 though from speaking to Mike over at SoundSplinter.

The FS is a little lower, but are you factoring the D2 and not the D4 RL-p? Anyway I like your approach and again am very interested in what you come up with. :cool:

I just put the figures in again (4ohm P) and get the same results, but now I'm starting to waffle, but I must resist the temptation to increase the budget.

I too am rather anxious to see how all this works out. At this point I'm determining suitable bracing and enclosure. Think I'll go thinner (1") on the exterior and spend more on the bracing reason being I've owned Yorkville Elite 18" pro bass bins used for gigging and I believe they were built from 15mm (approx 5/8") 11 ply birch but with extension bracing and these things were remarkably solid enclosures, rock-like in strength completely free of vibration or flex at silly SPL's. With that in mind I'm contemplating using 4 one inch thick shelf braces spaced every 6 inches (36" tall cabinet, 34" inside) on the horizontal plane all with one large central circular hole, the bottom brace further modified to make room for the drivers basket.

I discussed this issue of Titanic going slightly deaper with ThomasW. One of the reasons for getting the RL-P15 driver is that it can handle more EQ and LT to increase the low end. So yeah, the Titanic will go slightly lower when placed in the same box, but the RL-P15 will allow you to go lower and have more power if you use EQ or LT.

Understand your goals. Sounds good. You will want a little fill to absorb the high frequencies. I beleive that Thomas just told Steve this.

Man I'm a little slow here, opened the link to reply with my previous post then walked away for a few hours.

That makes perfect sense and is consistant with the modelling. The Dayton has far less excursion headroom at any given SPL at 20 Hz compared to SS.

This is a tough call for me, I'm taking a bit of a risk with the Daytons in my large room they just can't handle gobs of power down low when in a large box. My primary concern is getting decent room response from 30-80 or maybe higher for music, loud SPL's below 25 or so are not as improtant to me and could live with that compromise if the setup is great elsewhere.

Regarding absorption, I wasn't planning anything at this point, any idea what high frequencies Thomas was referring to?

1" side walls with plenty of bracing will probably work. I'm at 1 1/4" (3/4 + 1/2) with one brace, and can feel cabinet vibration. A glass with water on top will move around and splash the watter. But, I'm not sure how much it is hurting my SQ. I wish I would have added a little more bracing.

Do you have a source for 1" MDF? 3/4" is common. 1" is special order, I beleive. That is why a lot of people use two layers of 3/4".

Depending on your experance with expensive subs, you will probably be very very happy with the Titanic, but always have this lingering thought in the back of your mind, "I wonder how much better it would sound with an RL-P15." :)

I'm not sure of all the exactly sure of frequencies are that Thomas was refering to. Maybe check out Steve's thread over at HTguide.com and ask. But, even ported boxes have lining on the walls, for this reason, I beleive.

My primary concern is getting decent room response from 30-80 or maybe higher for music, loud SPL's below 25 or so are not as improtant to me and could live with that compromise if the setup is great elsewhere.

If this is the case then imo your going to be ok with the two Daytons. From my take on things, you have some experience behind you regarding bass so you might want to step it up to the RL-p for reasons Ryan suggests. There has been Dayton driver users who have and were glad they did.

I can honestly tell you my final outcome with the RL-p driver has provided me with the best bass I have had thus far..HT and music! I wouldn't attribute it just to the driver or the enclosure though. It was a combination of different components coupled with a decent encloser...3.8 cu ft 1.25" MDF with two braces and a third brace along the back of the second sub.. but hey! without a good quality driver you dead in the water. Running the sub with no EQ or BASSIS/LT for music is very doable if > (room permitting) mine sure is. It absolutely shines in a sealed enclosure for music. Since you have no problem going large (good for you) you'll have plenty of extension no doubt about it. I have great extension at 3.8, but have a 8-10dB dip to deal with at 17hz. If I meter from the other end of the couch, it's gone. Anyway thats been dealt with. I'm close to 100% HT and used to high SPL low FR teen response, so the BASSIS was called for along with adjusting the Q to just shy of .6

Regardless of what driver you go with, I would suggest a minimum of 1.25" thick MDF with not holding back on the bracing. 3/4 BB ply might be worth considering, but it runs up the cost of the enclosure. If you can handle it, I wouldn't hesitate on going the dual 3/4" layer of MDF though. I now have more respect concerning this suggestion along with plenty of bracing.

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But, even ported boxes have lining on the walls, for this reason, I beleive.

Some actually don't. Many only have a little strategically placed if any.

I have looked at the Stryke AV15 and I'm not sure if the parameters are correct from Stykes site but WinISD shows that to achieve .582 Qtc the box must be about 11.5 cubic feet vs Daytons 6.5. This is inconsistant with strykes charts so I'm not sure where the error is, other than that I like what WinISD is showing.. Not a significant difference from the Dayton, but regardless, I really don't like the aluminum cone which would prompt me to build a grill therefore adding more cost into the project.

I'm still somewhat undecided, Daytons 12" reference series drivers look very interesting as well, 4 of them may perform admirably.... the AV15 isn't completely off the list either.